The present invention refers to a connection device, particularly for connecting a flexible duct to a rigid duct, which is designed to be applied in a submarine system for petroleum exploration.
Connection devices as described above, also called xe2x80x9cplemxe2x80x9d, are already known. FIG. 1 shows schematically a system for extracting petroleum out of the bottom of the sea, with a Christmas tree 1 arranged on top of an oil well 2; a flexible duct 3 joining the Christmas tree to the manifold 4, and the latter being joined by means of a flexible tube 5 to a connection device 6, which in turn is connected to another connection device 7 by means of a rigid duct 8. The connection device 7 is connected by means of a flexible duct 9 to either a ship or a production platform 10, where petroleum is stored.
FIGS. 2 and 3 show, respectively, a side view and a top view of said connection devices 6 and 7 according to the prior art. These devices basically consist of a base 11, a hub 12 arranged horizontally, and a tube 12xe2x80x2 connected to the hub. At the free end of the hub 12 a flexible duct (5 or 9) is coupled, and the rigid duct 8 is connected to the tube 12xe2x80x2; the arrow 13 indicates the direction of petroleum flow.
A first drawback of the prior art consists in the following fact; as it is widely known, a rigid duct presents a much lower cost than that of a flexible duct. Thus, whenever possible, the installation of rigid ducts is preferred. According to the rules, the rigid duct 8 shown in FIG. 1 is constituted by joining various segments of tube welded to each other, which have a diameter of, for instance, 16xe2x80x3, 12xe2x80x3 or 10xe2x80x3. Each segment is 900 meters long and is made by welding 75 stretches of tubes, each of them measuring 12 meters. Thus, the service ship unloads onto the bottom of the sea the various segments of rigid ducts, which are joined later by submarine welding. After the connection of the rigid duct 8 on the bottom of the sea, its ends are hoisted and, on board of the service ship, the respective connection devices 8 and 7 are connected. Then a steel rope is tied to the eyelet hole designed for hoisting/launching the connection device, and the duct is launched again (an end at a time) onto the bottom of the sea.
However, the rigid duct often presents a residual torsion during its descent to be laid onto the bottom of the sea again. This torsion also causes a torsion on the connection device 6 or 7, which, at the end of the descent, lies on the bottom of the sea in an incorrect position, which renders substantially difficult the installation of the flexible ducts 5 and 9 and of the umbilical connections (details later and not shown in the figure) for command of the line. Frequently there are also cases in which, due to a very incorrect final position of the connection device, it is not possible to install the flexible ducts 5 and 9, and so one has to hoist each end of the rigid duct 8 with the respective connection device and to launch it into the sea again. Sometimes, various hoistings are required before the satisfactory position of the connection devices is achieved, which makes the installation of the system substantially expensive.
Another drawback of the prior art consists in that, in order to connect the ends of the flexible ducts to the respective connection devices 6 and 7, more than one hydraulic tools are required at different steps and, consequently, more than one maneuver with the service ship, which makes the operation of installing the extraction system extremely expensive and complicated.
There is a third drawback, which is detailed below. The ducts 5 and 9 are accompanied by electric cables and small hydraulic command tubes or umbilicals (not shown), which serve to command remotely, from the ship or production platform, the operations of the petroleum extraction system. This assembly formed by the duct, electric cables and hydraulic tubes is called line. However, during the connection of the lines 5 and 9 to the respective connection devices or plems 6 and 7, damage to the electric pins often occurs before they fit into the respective sockets. The same problem occurs with the hydraulic command tubes, the prominent ends of which are even more liable to be damaged than the electric pins. These problems occur mainly because the hub 12 is horizontally arranged, which renders the fitting of the elements difficult.
The objective of the present invention is to provide a connection device or plem which avoids the drawbacks above and reduces both the costs of installing the extraction system and the time of maneuver of the service ship and hydraulic tools.
This objective is achieved by the fact that the connection device comprises a base; a hub fixed onto the base; a hoisting/launching device, and a tube with the first end connected to the hub and the second end being free, the hoisting/launching device being placed above the center of gravity of the connection device and the second end of the tube is movable.
The end of the tube is rotatable and longitudinally displaceable with respect to the body of the connection device, and the hoisting/launching device may be, for instance, an eyehole.
The hub may be arranged either vertically or horizontally on the base, which is constituted by a central structure and two side structures, one on each side of the central structure, the side structures being turnable.
The movable end of the tube is lockable after the laying of the connection device onto the bottom of the sea by means of hydraulic oil applied under pressure in hydraulic command tubes.
In this way, in the connection device of the invention the hoisting/launching eyehole is above the center of gravity and the end of the tube to which the rigid duct is joined is rotatable. These characteristics enable said device to maintain its position during the descent to the bottom of the sea, thus compensating for the residual torsion of the rigid duct. This provides the great advantage that the connection device will always present a correct final positioning on the bottom of the sea, which prevents the drawbacks of hoisting and relaunching, as cited with respect to the prior art. This fact implies a substantial reduction in the costs of installing the system.
Another advantage of the invention consists in that, when the hub of the connection device is placed in the vertical position, the engagement of the flexible ducts, electric cables and hydraulic command tubes (umbilicals) which make up the line is effected much more simply and quickly. The installation of these lines is carried out with the aid of the vertical connection module (MCV), which is the object of other patent application, the applicant of which is also CBV Indxc3xastria Mexc3xa2nica S.A.